The present invention relates to an electromagnetic relay and, more particularly, to an inexpensive, small-height electromagnetic relay having a high breakdown voltage.
Conventionally, an electromagnetic relay is known in which the contacts are switched by driving an armature inserted in the hollow portion of a coil bobbin. Japanese Utility Model Laid-Open No. 5-94936 discloses a technique as the first prior art technique. According to this technique, a substantially flat plate-like armature is inserted in the hollow portion of a bobbin. A movable spring and the armature are connected to each other with a resin card so that the movable spring and the armature or a yoke will not come into contact with each other. The movable spring and the yoke are insulated from each other with a barrier integrally formed with a base. As a result, an electromagnetic relay having a high breakdown voltage between the contact and coil can be obtained.
The second prior art technique will be described with reference to FIG. 9. According to this prior art technique, a core 1003 is inserted in the cylindrical hollow portion of a spool 1001, and a coil 1002 is wound on the spool 1001 about the core 1003 as the center. One end of an L-shaped yoke 1004 is caulked at the lower end of the core 1003. One end of an armature 1011 supported by hinge springs 1009 caulked on the rear surface of the L-shaped yoke 1004 is in contact with the upper end of the upright portion of the L-shaped yoke 1004. The other end of the armature 1011 opposes the upper end of the core 1003.
The armature 1011 is connected to the hinge springs 1009 through a boss 1010. The other end of each hinge spring 1009 opposite to its hinge portion forms a movable spring 1008. A movable contact 1007 is formed on the distal end portion of the movable spring 1008. Stationary contacts 1006 are arranged to constitute a pair through the movable contact 1007. The opening portion of the case is sealed with an epoxy-based adhesive.
The conventional electromagnetic relay described above has problems as follows. The first problem is the high manufacturing cost. This is because the number of components is large.
The second problem is that the electromagnetic relay does not have a high breakdown voltage. This is because the excitation coil side (primary) and the contact side (secondary) are connected to each other through the space around the card.
The third problem is that the electromagnetic relay cannot be made compact. This is because the yoke needs a space for caulking the hinge spring stationary portion.